Pyrroles are known chemical compounds having a five-member ring structure wherein four of the ring members are carbon atoms and the fifth is a nitrogen atom. It is known that the carbon atoms may include substituents such as alkyl, alkene or halogen. The pyrroles may be di-substituted.
Polymerization of pyrrole is also known, and particularly electrochemical polymerization of pyrroles has been disclosed for instance in the J. Chem. Soc. Chem. Comm., pp 635 (1979). Polymerization of pyrrole at the anode of an electrochemical cell in the presence of a conductive salt gives films having electrical conductivity. Such resulting conductive polypyrroles include counter-ions, particularly BF.sub.4.sup.-, AsF.sub.6.sup.-, ClO.sub.4.sup.-, and HSO.sub.4.sup.-.
Typically, production of polypyrrole film-like structures is conducted by electrochemical polymerization in a conventional electrolysis cell that may optionally include a diaphragm, employing noble metal electrodes. Platinum or valve metal electrodes such as titanium are typically preferred. The resulting polypyrrole film formed by anodic oxidation is deposited on the anode and subsequently removed by stripping. Methods for continuously forming a film like structure and continuously stripping the structure from an anode have been suggested, for example, in U.S. Pat. No. 4,468,291.
It has been noted, however, that electrolytically formed polypyrrole films, particularly those including the HSO.sub.4.sup.- counter-ion, tend to relative brittleness when formed, and to an increase in brittle character with the passage of time.
Since polypyrroles have desirable resistance to chemical attack and can therefore provide or impart chemical resistance properties to objects forming or contained within a structure enclosed by polypyrrole. But where through embrittlement, the structural polypyrrole cracks or becomes otherwise discontinuous, the capability for the polypyrrole structure in providing protection from chemical attack may be substantially reduced. Where electrically conductive polypyrroles are employed to provide a coating over a substrate thereby enhancing electrical conductivity over the substrate, cracks and other defects in surface characteristics of such a polypyrrole coating could substantially interfere with effective and desirably uniform electrical conductance characteristics. Particularly where polypyrroles are structurally employed in the form of a film subject to frequent movements of even miniscule magnitude, flexibility and a relatively non-brittle characteristic can be important to adequate performance of such films.
A method for enhancing the flexibility of structures, particularly films, comprised of polypyrroles could find substantial utility in the application of polypyrroles to products in industry.